<PAGE>
 
                                 SCHEDULE 13D

Cusip No. 294037205                           

1.   Name of reporting person
     S.S. or I.R.S. identification no. of above person

                        ZAPATA CORPORATION

2.   Check the appropriate box if a member of a group        (a)  [_]
                                                             (b)  [_]

3.   SEC use only

4.   Source of funds

 
                        OO
 
5.    Check box if disclosure of legal proceedings is required
      pursuant to items 2(d) or 2(e)                              [_]

6.   Citizenship or place of organization

                        Delaware

<TABLE>
<CAPTION>
 
<S>                       <C>  <C>                       <C>
 
          Number of       7.   Sole voting power         4,189,298
             Shares
       Beneficially       8.   Shared voting power each        -0-
           Owned by
   Reporting person       9.   Sole dispositve power     4,189,298
               With
                          10.  Shared dispositve power         -0-
</TABLE>

11.  Aggregate amount beneficially owned by each reporting person

                        4,189,298

12.  Check box if the aggregate amount in row (11) excludes
     certain shares                                               [_]

13.  Percent of class represented by amount in row (11)

                        31.0%

14.  Type of reporting person

                        CO